Method of making a heat exchanger



n 8 1940- R. s. NELSON ET AL METHOD of MAKING A HEAT EXCHANGER OriginalFiled June 29, 1955 [endow] .stwlm BY AI'IlO/d {91 81118 ATTQRNEYPatented June 18, 1940 PATENT OFFICE f METHOD OF MAKING A HEATEXC'HANGER Rudolph S. Nelson, Larchmont, N. Y., andArnold D. Siedle,Canton,

Ohio, assignors to The Hoover Company, North Canton, 0hio,-a corporationoi Ohio Original application June 29, 1 935, Serial No. 29,008. Dividedand this application May 16,

1938, Serial No. 208,278

9 Claims.

This invention relates to a heat exchange device, and more particularlyto a novel methodof constructing and fabricating such a device.

This applicationis a division of our copending application for LettersPatent, Serial No. 29,- 008, filed on June 29, 1935.

The construction of a' heat exchanger in large quantities from standardstock materials and in accordance with present day mass productionmethods presents several serious problems. This is especially true ofheat exchange devices of the finned-tube type where a very large numberof heat conducting fins must be placed on tubing in a uniform manner andin such 'a way as to insure a permanent bond of maximum heat conductingcapacity. j

Previous methods of construction involve either a large number of jointsbetween individual sec, tions of finned, straight sections of tubing, orthe transfer of individual fins over long sections of tubingin whichthere are return bends. Both methods are obviously disadvantageous, thefirst method involving a. large number of costly joints, and the second,an almost worthless bond between the fins and the tubing.

The present invention entirely avoids the disadvantages of prior'knownmethods of constructing finned-tube heat exchangers, and at the sametime provides a product which is much more economical to fabricate aswell as one which is much more efficient in operation, all as will bemore fully described hereinafter. f

It is accordingly an object of the presentinvention to provide a newmethod of making a finned-tube type heat exchanger having a large amountof heat-radiating surface and wherein the heat-radiating surface is soarranged that heat is transferred more effectively between the deviceand the fluid passing thereover.

Another object of the invention is to provide a new method ofconstructing a finned-tube heat exchanger having a minimum number ofjoints and in which the fins are pressed axially along only straightsections of tubing.

A still further object of the invention is the provision of a mode ofconstructing a continuous, finned-tube heat exchanger in which straightportions of tubing are simultaneously passed through a plurality ofheat-radiatingfinm and thereafter the tube ends are joined to anothersimilar heat exchange assembly comprising at least one similarly finnedstraight portion of tubing and in such manner as to provide a continuousfluid passage through the tubing.

Another object of the invention is to provide a (0!. sea-157.3)

finned-tube heat exchanger in which a continuous fluid path is providedwithin the tubing which tubing is slightly inclined to the, horizontal,and in which the fins are slightly inclined to the vertical so as toresult in more intimate wiping contact between a vertically-risingmedium and said fins and thereby more eificient heat transfer.

A further objectof the invention is a new mode of constructing acontinuous, finned-tube heat exchanger having a minimum number of jointsand in which all fins may be identical and in which the individualsections of tubing may be identical. A still further object of theinvention is the provision of a simpler, more efiicient and less costlyheat exchange device which is eminently adapted for mass production.

Other objects and advantages reside in certain novel features of thearrangement and construction of parts as will be apparent from thefollowing description'taken in connection with the accompanying drawing,in which Figure 1 is a side view of a coil of pipe constructed inaccordance with the principles of the invention and illustrating oneform thereof:

Figure 2 is an' end view of the coil assembly shown in Figure 1, theview being taken from the left of Figure 1;

Figure 3 is a fragmentary plan view of the ararrangement of Figures 1and 2; I

Figure 4 is an end view of a modified form of the invention; and CFigure 5 is a fragmentary perspective view of an assembly of pipes andheat-radiating plates used in the device of Figure 4.

In describing the structure shown in the drawing, it will be assumedthat the device is to be used to discharge heat from a fluid therein tothe atmosphere, as when used as an air-cooled condenser or absorber forrefrigeration apparatus. It will of course be understood that theinvention is intended for general application in exchanging heatbetweenfluids flowing out of contact with one another.

Referring to the drawings in detail and first to the arrangementillustrated in Figures 1, 2 and 3, it will be seen that a coil assemblyis shown as constructed of a number of pieces of pipe designated ii to09, inclusive. together with a number of heat-radiating plates or fins,the plates of one series being designated in, and the plates of anotherseries being designated 22. The pipes or sections of tubing H to l9inclusive are somewhat similar in shape, each having a long straightportion with a hook or reverse bend at one end thereof. Hence,theindividual sections may be said to comprise bent and unbent portions.It will be noted however that in the embodiment shown in Figure 1, thebends of certain of the pipes have difierent lengths thanthose of'others of the pipes. As is best shown in Figures 2 and 3, the bends onthe pipes or sec-' tions I2 and I6 are of the same length and are theshortest of any of those in the coil assembly. The pipesor sections ll,l3, l5, l1 and I9 have bends of the same length, these bends beingslightly longer than those on sections l2 and I6. Sections l4 and I8have bends of the same length, these being still longer than those onsections l3, l5, l1 andlfl.

The heat-radiating fins 2| and 22 are identical in construction. In thearrangement illustrated each is provided with five holes thereinarranged in offset or staggered relation, three of the holes being nearthe lefthand edge of the fin as viewed in Figure 2, and two holes nearthe right- .hand edge thereof. In making up the coil the pipes orsections of the series II to I9, designated by the odd numerals arepassed successively through the openings in the fins or plates 2|, allof the hook-shaped or return bend portions being on one end, as the leftend in Figure 1. Thus, the straight or unbent portion of section it ispassed through the upper holes in the plates 2|, the straight or unbentportion of section I3 is passed through the next lower holes in theplates 2|, and so on.

Inasmuch as there are relatively few fins to be pressed upon a givenstraight portion of a given section, and since even the first fin ispassed along the conduit for only a short distance, the bond between thefin and the conduit is so good that soldering, brazing or other positivebonding operations may not be necessary. Moreover, the openings in thefins are not distorted and enlarged as is the case where the fins arepassed over bent portions of conduit as has been common practiceheretofore.

Likewise conduit sections of the series H to I9 designated by the evennumerals have their straight or unbent portions passed through openingsin the plate 22, the bent portions of the sections being to the right ofthe assembly as viewed in Figure 1.

After the sections have been assembled in the plates 2| and 22 asindicated above, the end of each straight portion of a section is weldedto that end of an adjacent section which is near a bent or returnbend-portion of said section. In the drawings, the welds are indicatedas being merely butt welds, but it is obvious that one end of each pipemay be flared slightly to overlap the end of the succeeding pipe withwhich it is connected so that a lapweld can be made.

To complete the assembly a piece of straight pipe 23, which may be partof a refrigerating system, may be passed through the lower holes in theplates 22 and be secured as by a weld to the lower bent portion ofsection I9. Likewise a.

that as the sections are welded together a coil inclination of plates22.

is formed in which a downward substantially uniform slope is providedthroughout its entire length. In this connection it may be noted that Ithe inclination of the bent portions of the sections to the horizontalmay be and preferably is l the same as that of the unbent portions.Because of the inclination of the pipes the heat radiating plates 2| and22, which are disposed at right angles to the pipes passing through theholes therein are .also disposed in an inclined position, theinclination of plates 2| being in opposite direction from the vertical,from the Thus, when heat is discharged to the atmosphere from the coiland from the plates, air tends-to rise vertically through the coil, butis deflected from the vertical by the inclined fins. Because of thecontinued tendency of the cooling air to rise vertically, it will beclear that the air passes in close wiping contact with the fins therebyproviding highly efficient heat exchange.

A modified form of the invention is shown in Figures 4 and 5. In thesefigures the heat-radiating plates, only two ofwhich are shown forsimplicity in illustration, 'are formed by cutting a rectangular plateinto two pieces so as to form complementary plates designated 25 and 26,the plate 25 having a V-shaped or triangular shaped righthand edge asviewed in Figure 4, while the plate 26 hasa complementary depressed orrecessed V-shaped lefthand edge.

As in the arrangement of Figures 1 to 3, the

coil assembly of Figures 4 and'5 is made up from of two straight orunbent portions interconnected by a bent or return bend portion.

Sections 3| to 4| inclusive may be divided into two groups, those whichhave long bends or hooks and those which have short ones. The

pipes may be assembled from two different stocks,

the sections 3|, 33, 35, 38 and 40 each having long bends of the samelength, while sections 32,- 34, 36, 31, 39 and 4| each have bends of thesame length and shorter than those of the first mentioned group. As inthe arrangement previously described, the sections designated by the oddnumerals of the series 3| to 4| are assembled with a number of plates 25by passing the straight or unbent portions through holes in theseplates. the sections designated by the even numerals 32 to 40 are passedthrough holes in a number of plates 26. It will be noted that the holesin the plates 25 and 26 are disposed along the inner V-shaped edgesthereof and at equal distances from these edges. The assembly of thesections and two of the plates is illustrated by the arrangement inFigure 5, it being understood that in this figure, while only one ofeach of theplates 25 and 26 is shown, a number would be employed in thecomplete assembly. As shown in Figure 5, the sections designated by theodd numerals At the same time,

3| to 4| have their bent portions below the plate 25 while thesectionsdesignated by the even nu-v merals 32 to 40 have theirbentportions above the plate 26.

After the sections have been assembled with the heat-radiating plates,they are welded together to form a coil as described hereinaboveinconnection with the arrangement of Figures 1 to 3. Conduit 42, Figure 5,corresponds to conduit 23 of the embodiment shown in Figure 1.

Since each straight portion ,of the sections of the series 3| to 4| isinclined downwardly slightly to the horizontal plates 25 and 26 areinclined with respect to each other and each is inclined slightly to thevertical. This relationship is shown exaggerated in Figure 5 for purposeof illustration, the true inclination of the plates 25 and 26 in thecompleted assembly being somewhat similar to the inclination of theplates 2| and 22 in Figure 1.

Because of the peculiar shape of the inner edges of the plates 25 and26, the arrangement of Figures 4 and 5 has a particular advantagein thatas heat is discharged from the coil and from the plates 25 and 26 to theatmosphere, air is caused to pass upwardly through the coil and in sodoing, is deflected from one heat-radiating plate to the other,especially along the inner edges thereof, so as to cause air to come in heattransfer relation with these plates and with the. coil.

From the above description, it will be clear that two forms of theinvention have been illustrated in which a coil is assembled and con-,structed in a novel maner and in which a large heat-radiating surfacehas been provided. Such a coil could be used to particular advantage asa condenser in a refrigerating system. When so used, the gas to becondensed might be supplied to the upper end of the coil and as itcondenses be drained away as a liquid through the lower connectionthereto. The coil might be used as an absorber or other vessel of arefrigerating system also, or in any place where a transfer of heat toor from a fluid in the coil is desirable.

While only two embodiments of the invention have been shown anddescribed herein, it is obvious that various changes may be made withoutdeparting from the spirit of the invention or the,

scope of the claims;

We claim: 7 a

1. The method of fabricating a continuous finned-coil heat exchangercomprising, placing return bend loops in one end of a plurality ofsimilaruconductors, dividing the conductors so formed into twosubstantially equal groups, inserting the. unlooped ends of each groupinto snuggly fitting, staggered openings in a plurality of similarmembers of high heat conductivity, and joining the looped ends of onegroup with the unlooped ends of the other group in such manner as toform a continuous passage of varying elevation from the inlet to theoutlet of the heat exchanger.

' 2. The method of fabricating a continuous, finned-coil heat exchangercomprising, placing return bend loops in one end of a plurality ofsimilar conductors, dividing'the conductors so formed into a pluralityof substantially equal groups, inserting the unlooped ends of each groupinto openings in a plurality of closely spaced similar members of highheat conductivity, said members being common to the conductors of agiven group of conductors, and joining the unlooped ends of one groupwith the looped ends of another group in such manner as to provide aheat exchanger having a continuous fluid passage of gradually varyingelevation from one end thereof to the other.

3. The method of fabricating a continuous, coil heat exchangercomprising, forming return loop bends in one end of a plurality ofconductors,

inserting the unlooped ends of each group through snugly fittingstaggered openings in a plurality of plates of high heat conductivity,the plates being positioned at right angles to the axis of theconductors, and joining the looped ends of one group of conductors withthe unlooped ends of another group in such a manner as to provide a heatexchanger having a continuous passage of gradually varying elevationfrom one end thereof to the other and in which, in one position of theheat exchanger, all portions of the passageway are at a slight angle toa horizontal plane and the plane of the plates is at a slight angle'to avertical plane.

4. The method of making a heat transfer device adapted for use in arefrigerating system, the method including the steps of bending a numberof straight pipes to provide hooks on one end of each, making a numberof heat transfer plates with holes therein,.the adjacent holes beingstaggered with respect to one another, passing the straight portions ofone set of pipes through the holes in one set of plates so that thepipes are offset from one another, passing the straight portions ofanother set of pipes through the holes in another set of plates so thatthese pipes are also staggered with respect to one another and weldingthe ends of the straight portions of each set of pipes to the ends ofthe hooks on the other set of pipes to form acoil with heat transferplates thereon.

5. The method of constructing a heat exchange device of the finnedconduit type in which the individual fins-are passed axially alongtubing and in intimate heat exchange relation thereto,

slightly less than and a shape corresponding to the cross sectional areaof tubing on which the fins are to be placed, cutting lengths of.straight conduit into short sections, pressing a, plurality of said finsalong a plurality of said sections in spaced, parallel relation to oneanother, arranging said sections in side by side relation laterally ofand generally parallel to one another -with alternate sections inclinedto the horizontal in one direction and the remaining sections inclinedto the horizontal in the opposite direction, and joining the adjacentends of said finned sections directly to one another so that theportions of the sections interconnecting the generally parallel portionsof said sections are inclined slightly to a horizontal plane to providea continuous fluid path from one eind of the conduit to the other whichis inclined to the horizontal substantially uniformly-throughout itslength.

6. The method of construction a heat exchange device of the finned tubetype comprising cutting a straight length of tubing into a plurality ofshort sections, placing a bendin one end of each of said sections,inserting a plurality of similar spaced-apart fins over said sectionssothat the fins are perpendicular to the axis of said sections,

arranging said finned sections oftubing in side by side relation, andgenerally parallel to one another, and joining the bent ends to theunbent ends of adjacent sections of tubing in such manher as to providea single continuous downwardly inclined passage'from one end of the heatexchange device to the other, said tubing sections being so disposedbefore being joined that alternate sections are inclined to thehorizontal in' one direction and the remaining sections are inclined tothe horizontal in the opposite direction whereby the fins on alternatesections are inclined to the vertical in one direction and the remainingfins are inclined to the vertical inthe opposite direction. v

'7. The method of constructing a heat exchange device of the finnedconduit type in which the individual fins are passed axially alongtubing and in intimate heat exchange relation thereto,

comprising piercing a plurality of fins of high heat conducting materialwith openings of a size slightly less than and a shape corresponding tothe cross sectional area of tubing on which the fins are to be placed,cutting lengths of straight conduit into short sections, bending theopposite ends of the short sections toward each other to form a returnbend, pressing a plurality of said fins along the unbent portions ofsaid sections in spaced, parallel relation to one another, arrangingsaid sections in side by side relation so that the straight portions ofsaid sections are positioned laterally of and generally parallel to oneanother with alternate straight portions of said sections inclined tothe horizontal in one direction and the remaining straight portions ofsaid sections inclined to the horizontal in the opposite direction, andjoining the adjacent ends of said finned straight portions of thesections directly to one another so that the portions of the sectionsinterconnecting the generally parallel portions of said sections areinclined slightly to a horizontal plane to provide a continuous fluidpath from one end' of the conduit to the other which is inclined to thehorizontal substantially uniformly throughout its length.

8. The method of constructing a heat exchange device of the finned tubetype comprising cutting a straight length of tubing into a plurality ofshort sections, placing a return bend intermediate the ends of each ofsaid sections so that each section comprises two straight portionsv anda return bend portion, inserting a plurality of similar spaced-apartfins over straight portions of said sections so that the fins areperpendicular to the axis of said sections. arranging said finnedsections of tubing in side by side relation and generally parallel toone another, and joining the end of one section to the end of anadjacent section of tubing in such manner as to provide a singlecontinuous downwardly inclined passage from one end of the heat exchangedevice to the other, said tubing sections being so disposed be- 'forebeing joined that alternate straight portions of the sections areinclined to the horizontal in one direction and the remaining straightportions of'the sections are inclined to the horizontal in the oppositedirection whereby the fins on alternate straight portions of saidsections are inclined to the vertical in one. direction and theremaining fins are inclined to the vertical in the opposite direction.

The method of constructing a heat exchange device of the finned conduittype in which the individual fins are passed axially along tubing and inintimate heat exchange relation thereto, comprising piercing a.plurality of fins of high heat conducting material with openings of asize slightly less than and a shape corresponding to the cross-sectionalarea of tubing on which the fins are to be placed, cutting lengths ofstraight conduits into short sections, bending the opposite ends of theshort sections toward each other to provide two unbent portions and areturn bend portion between the opposite ends of said sections, saidunbent portions extending from said return bend portion at an angle toone another; pressing a plurality of spaced-apart, parallel heatdissipating; fins axially along at least one of said unbent portions ofeach of said sections, said fins being positioned perpendicularly tosaid unbent portions, arranging said sections in side-byside relation sothat the unbent portions of said sections are positioned laterally ofand generally parallel 'to one another with alternate, consecp utive,unbent portions of said sections inclined slightly to the horizontal inone direction and the remaining alternate unbent portions of saidsections inclined slightly to the horizontal in the opposite direction,and joining the adjacent ends of said unbent portions of the sections toone an- 40 other to provide a single continuous coil heat exchangerhaving a continuous fluid path from one end of the conduit to the otherwhich is inclined slightly and substantially uniformly to the horizontalthroughout its length.

RUDOLPH S. NELSON. ARNOLD D. SIEDLE.

